This invention relates to acoustic barriers for vehicles and more particularly to an improved acoustic barrier system for reducing transmission of noise from the engine compartment of a vehicle into the passenger compartment.
It has been a common practice in the automotive industry to employ a double wall barrier system to reduce noise from the engine compartment to the passenger compartment of a motor vehicle. The acoustic barrier system generally comprises a steel wall separating the engine compartment from the passenger compartment and a dash barrier spaced away from the passenger compartment side of the steel wall. A foam or fiber sound-absorbing material is typically disposed in the space defined between the steel wall and the dash barrier.
The heater case, frequently referred to as the HVAC (heating, ventilation and air conditioning) unit, is installed in the passenger compartment over the dash barrier. Apertures through the steel wall and dash barrier are provided for tubes used to convey engine coolant or refrigerant to and from the HVAC unit. Foam seals are used to fill any spaces between the tubes and the openings for the tubes to reduce the amount of noise entering the passenger compartment and to prevent water or other materials from entering the passenger compartment. However, as is frequently the case with components that are required to perform multiple functions, the foam seals do not perform both functions as effectively as may be desired. In particular, the seal must exhibit optimum moisture sealing properties, with acoustic barrier properties being of secondary importance. As a result, there is a need for more effective noise reduction than has been provided by conventional foam seals that have been used at refrigerant tube openings through the double wall barrier. A similar need for improved noise reduction exists at other pass-through openings for conduits to vehicle components, such as electrical control boxes, mounted in the passenger compartment adjacent the acoustic barrier.
U.S. Pat. No. 5,557,078 discloses an acoustic barrier for a wall having an opening with a conduit, such as a hose, cable or wire, passing through the opening and an article such as an electrical control box mounted on one side of the wall. A moisture seal is located in the wall opening, and a mass layer of resilient or flexible plastic (e.g., filled thermoplastic olefin) is positioned adjacent the wall. The mass layer includes a support rib defining an opening in the mass layer in registry with the wall opening and surrounding the article. The mass layer further includes a flexible seal extending inwardly into the mass layer opening from an edge thereof in contact with the article to provide an acoustic seal around the article. In the disclosed embodiment, the flexible seal comprises a plurality of flexible flaps separated from each other by slots. The flexible flaps are resilient and bear against the article to form the acoustic seal between opposite sides of the wall.
The only illustrated embodiment in U.S. Pat. No. 5,557,078 is for a relatively small electrical control box having a back wall that completely abuts against the moisture seal, with the flexible flaps engaging against top, bottom and side walls of the electrical control box. Thus, the disclosed acoustical barrier appears to have limited application. Accordingly, there remains a need for an improved acoustic barrier system for reducing noise transmission from the engine compartment to the passenger compartment at conduit pass-through apertures, which is useful in a variety of different applications.
The invention provides a secondary acoustic barrier to reduce the amount of noise entering the passenger compartment of a vehicle. In particular, the secondary acoustic barrier extends from a primary acoustic barrier to a vehicle component case to envelop space around a conduit passing from the engine compartment to the component case.
In one aspect of the invention, a vehicle comprises an engine compartment, a passenger compartment, a metal wall separating the passenger compartment from the engine compartment, and a primary acoustic barrier disposed adjacent the metal wall. An aperture is defined through the metal wall for passage of a conduit, and an aperture is also defined through the primary acoustic barrier for passage of the conduit. The aperture through the primary acoustic barrier is in registry with the aperture through the metal wall. A case for a vehicle component is mounted in the passenger compartment adjacent the primary acoustic barrier, and a moisture seal is used for sealing between the conduit and the metal wall. In order to achieve improved noise reduction in accordance with the invention, an acoustic attenuator extends from the primary acoustic barrier to the component case to envelop space around the conduit between the component casing and the primary acoustic barrier.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.